US Patent 7419432 Coupling joint structure of small-sized boat

A coupling joint structure for a boat where the output of an engine can be securely transmitted to a propeller shaft and centrifugal force can be reduced. The structure includes a first coupler on the driving side to an output shaft, a second coupler on the driven side to a propeller shaft, and a damper member interposed between the second coupler on the driven side and the first coupler on the driving side. The first coupler on the driving side and the second coupler on the driven side each include pawl pieces. In a first curved part of each of the pawl pieces on the driving side, the base (wall thickness t1) is made thicker than the end (wall thickness t2). In a second curved part of each of the pawl pieces on the driven side, the base (wall thickness t1) is made thicker than the end (wall thickness t2).